LOTS OF HOW TO CHOPPER PROJECT REPORTS... We build choppers the old school way... craftsmanship and artistry. Photos of our work to give you ideas... Aftermarket parts, parts for Shovels, CB's and XS's, our own unique parts for sale...

Owner had hoped to put it into a stock Triumph frame like this, but...

it is not to be because the story so far is...

An entire Thunderbird was purchased by the owner as a statutory writeoff. He had thoughthe'd be able to import a stock frame from the US (which he had lined up). However SA road regs do not allow a statutory writeoff to be rebuilt with a stock floor pan (car) or stock frame (m'cycle). It can only go into a CUSTOM frame.

We had the engineer up and he felt that for him to a pass mild steel frame that is a copy of the original frame made of high tensile steel, would be very difficult and would need testing.

His suggestion instead was that we chase up a custom HD frame and see if we can fit the engine into it.

I contacted Attitude Motorcycles in Vic and looks like this is the way to go. Because their frame will already acceptable with MSO etc and is designed for a similar size motor (1700cc) we should have no problems with engineering.

I am sending the original frame (undamaged) and swing arm to Attitude and they will set up the frame to suit... then send it back and we will build engine mounts and all the other stuff so owner can put it together.

Owner wants it as close to the original set up as possible, rake, length, seat and frame height etc., so it won't be a chopper or bobber but...

It will be something different and a bit of fun... definitely better than trying to replicate the original monstrosity.

We'll keep you informed once we get the frame back and can get a start on it.

Well the plot thickens. Seems like a major calamity has occurred at Attitude and our frame is being returned without any work being done.

I am currently considering a KraftTek FXR frame, but awaiting an email reply as to whether the Triumph right side rear drive will foul the frame. If it does, then we'll go to another alternative which is to build a frame from scratch, but copy the KraftTek loop frame style instead of trying to copy the original frame.

Lots more phone calls and emails. Motor is a tad too high as the engine sump is too wide to fit between the standard HD lower cradle rails. We still can't find out clearance around the swing arm mounting, so it's been decided that we will build a new cradle frame to match. Similar rake, possibly slightly lower.

Engine and frame/swingarm/forks being mocked up tomorrow and engineer calling in on Thursday, so he can get some dimensions to check against his tables... and then we'll get stuck into it.

Amongst a pile of other things, we set up a basic mockup of the project today.

We set the motor up yesterday. Wayne was worried how we could get it up onto the blocks I set up. Aha Wayne! Working by myself over many years results in a few little tricks. A ramp out of melamine (slippery surface) makes the move a breeze... a one person job with no strain on the back muscles...

Motor is now blocked up to height it wlll be when complete. Ground clearance was obtained of the net. For the actual build we will set it an inch higher to allow for sag of suspension...

Next is to fit the main bits around the motor to see what lines the frame can take...

I've spent some time looking at the most appropriate frame design for this machine... swing arm to steering head line needs to be as direct and stiff as possible. Swing arm mount needs to be sufficiently strong so prevent even the slightest twist under hard acceleration which would pull belt out of alignment and wear it excessively. Whole frame needs to be stiff... the motor has tons of torque.

I've been flat out and had no time to post. Jason's twin Cam chopper is home and awaiting a trip to Regency. We fixed up a repairable write off for Triumph America for Jett. Also awaiting Regency. Jon has a new narrow glide front end on his sporty. Lots of small jobs done... and of course major movement on this Thunderbird.

We got the engineer up and looked at frame configurations and settled on a loop frame that will look something like the mockup below. Major consideration is to have something that will stand up to the torque of 1600cc, allow the motor to be easily removed... and look good.

Frame tubing is 1.25" x 3mm wall 250mpa DOM. Higher mpa (mild steel tube is normally around 120mpa) means a 'denser' that will resist stretching (and therefore thinning of the wall thickness. Wayne also began wanting the bike to look exactly like the original and be able to fit all parts including many pieces of tin ware and big lupms of castings to carry exhausts etc.

However I managed to convert him somewhat as we proceeded with the planning. What we settled on was using the same tank (though it will have to sit a couple of inches higher and also the original seat and air/batter/electrics box. He did still hope to use some of the covers, but gradually realised that the frame needs to be fully seen and become a feature of the bike. We are legally able to use Triumph front end and swing arm and shockers and of course the wheels.

Machining was first job. Steering head, headstem and the rear engine mounts and swing arm mounts. The original mounts are threaded for an adjusters that wind up against the engine and the swingarm. Here you can see the old bent headstem and the new one which is a tight press fit.

Outer bearing races need to be removed to measure ID of steering head. One came out easily, but the other needed a bead of weld to shrink it... just about drops out then...

Large hollow bar was used to make steering head. To support it length in the lathe chuck, I had to make up a plug to tap into the end. Hollow bar can now be supported at both ends while machining...

Bearing out cup surfaces now machined using a boring bar...

Measuring, measuring, measuring... If there is one thing we've done more of than anything else its been measuring and rechecking measurements. No good building a frame and then not being able to remove the motor or the air/battery box or have the radiator foul the forks and wheel. And of course it all needs to be aligned and sit at the right height etc, etc, etc........... etc...

I should also mention that this thread will not have the build detail of other threads as it is not a chopper. However, I thought it worthwhile to put in some detail as there are things you can apply to your own builds.

One important thing to keep in mind is to know what you are doing or get advice when building structural parts of a chopper. Frames are not just a bunch of pieces of odd tube welded together. Locations of joints, gusset thickness, shape and placement, tube thickness and diameter, weld positioning, length and penetration can not be haphazard if you want to build a safe chopper (well you do don't you, though I have met a few who don't care or are too afraid they might lose face if they ask for advice).

Wheel, steering head and chain/belt alignments are also crucial.

Just getting the motor and the swing arm and steering head set up and aligned on the jig took around 15 hours of solid work and measurement...

To easily remove the motor, I settled on 1. lift the front, 2. slide it forwards an inch and lift the whole lot an inch and then slide it out. This determined distances of the frame tubes from the motor. It also determined the shape and method of engine mounts (top and top rear are removable clevises) and the swing arm plates on each side.

On the original set up, removing the airbox required removal of the swing arm. Although once it is finished the box will not need to be removed, construction is a different matter and at the stage we are now at (see bottom pic) we have installed and removed the box at least 20 times. So this was another consideration that took time and planning.

To move the motor forwards meant moving the front down tubes forwards 1.5". The radiator sits in front of these, so the steering head had to come forwards the same amount. Because that would put the handlebars forwards and Wayne is somewhat height challenged like myself I added two degrees to the rake to tilt the bars back to the rider. This of course drops the front end, so we did some calcs on the cement floor and dropped the steering head 20mm.

We'll see if we got it right next week when we finally get it on its wheels. Yippeee!

Steering head mounted and located in jig. Measuring from two established points on the old frame and then the positioned motor is necessary for all these bits...

Steering head also has to be centred. Juts centring the motor was difficult because very little of it gives any incitation of a centre point. We had to work it out by measuring off the centre of the rear wheel to the belt drive pully and centring the motor with that and then squaring it up using the left side machined edge of the engine case.

Here you can see spirit level and plumbob used to centre steering head and at the bottom of the pic the red spot of the laser to align the steering head...

Setting up the first downtube/lower frame rail. Threaded rod front and back of the motor was used to get it perfectly positioned after which mounts were built and bolted in under motor. Bottom rails also have to clear mounting holes for footboards and allow room for the exhausts. They also have to clear exhausts at heads... more measuring and double checking.

Had to extend the bender to give it enough height to fit this sucker. This bend is the turn in that meets the shocker mounting plates...

You can also see the separately mounted swing arm and the jig made up to locate top shocker mounts...

White 1" flat bar sets distance forward of down tubes as they get bent and fitted. Springers in backgound belong to a KZ750 build and a CB750 Build...

Cross pieces on frame were positioned to allow them to be used as a levering point for engine removal and installation. A large callipers (make your won using a couple of pieces of flat bar with a bolt and wingnut for the pivot or go to a few swap meets) is used to measure length. Measure between down tubes and then add 5mm to each side for the curve...

Fuel tank is a wide beast and has the fuel pump mounted centrally in the bottom . Top tubes have to bend around this. On the original frame, the top tubes turn back in and almost touch. Too many bends too close together for us. The tank will have to sit a bit higher, but though it will raise the centre of gravity an inch or so, the rider will feel more secure, sitting down in behind the tank. More checking to see that the radiator filler cap on the end of a piece of solid bent tube can fit...

Arrows point to where frame tubes are welded to extensions to the jig. Seat fits to an opening on the airbox and has to fit in front of the rear frame rail. More measuring to make sure seat will line up perfectly. You can also see one of the machined bungs that support the swing arm...

Wayne machined up the threaded shocker mounting bungs...

Steering head gusseting. Care needs to be taken when welding as the heat expands the metal and shrinks it slightly more when it cools. Tack welding letting tacks cool befor further welding helps a lot...

These two curved tubes prevent the top tubes from pushing down under pressure. They purposely attach lower than the steering head gussets to spread the load and reduce stress points...

We used to always joke about how the Brits built bikes in the fifties; they'd tack up the frame and put the motor in then move the frame tubes and fittings to make sure 50 percent of the motor bolts were inaccessible!!!

Every step of the way things are checked to make sure components fit or can be adjusted/maintained etc. Here making sure spark plugs can be accessed...

Front engine mount patterns. Cross bar serves three purposes; strengthen frame, provide a second plane of support for the engine mount and provide an attachment point for the mount...

Front view of the mounts (8mm) which also double as the bottom radiator suppport...

Stock plates that support rear guard and shockers are traced onto cardboard and cut out, then cut out of 8mm steel plate...

Rear frame rails are given final alignment with mild heat using this very handy lever. When a tube bends, the outside of the bend stretches and the wall thins slightly. You reduce this thinning effect by heating the outer area over a wide area. When heated steel cools, it shrinks slightly pulling out of original alignment (this principle is used in panel work). Therefore when bending a tube to align it, heat the inside once it has been bent to even up the cooling. This way you can maintain the new position...

Rear shocker/guard mounts tacked into place. Air box is in place so a rectangular cross piece can be measured and set up. This will carry the airbox and seat mounts...

A side view so far... which for Wayne especially was very exciting... seeing at last what the frame was going to look like. The 3mm wall rectangular tube sitting ready to be shaped...

Air/battery box hangs of the rectangular cross piece. A pair of M6 bolts are welded in. Hole on topside is countersunk to leave a flat surface for seat mount.

Top engine mount needs to be removable so engine can be lifted. A rectangular cross piece (25x50x3) is drilled to take a pair of 8mm bolts. The removable bracket is done in 8mm x25mm bar. A spacer fits on the left side (right in pic) to allow the water filler tube to be installed and removed. Throttle cables also have to fit through here. Their route and location of their lock nuts determined the rearward position of the cross piece. Took a bit of mucking around to get this worked out.

Top steering head gusset also carries the front mount for the tank. Mount has a narrow lip machined into it to locate the rubber mount of the tank...

Ladder gets used a number of times...

Gusset and mounting lug...

Rear mount of tank was able to be used though it had to be bent about 60 degrees downwards to clear the seat...

Pretty tricky hey? Tank swings up to allow access to water filler and plugs...Tank was mounted to clear the frame by 4mm, Arrows show three of the four rubbers temporarily mounted on frame tube to get spacing right...

Once seat mount was made, seat rails could be cut and fitted...

These side plates carry the two rear engine mounts and the swing arm. The plates were first shaped and tacked in place, then the machined mounts were cut and linished to fit and tacked on the inside. Side plates were then removed, the mounts welded in. Then onto Herb (big geared drill) to be drilled through from the inside and then enlarged from the outside to fit the bolt heads. The top bulge on the plate is to locate a cross member to which the final engine mount will be attached...

Here all fitted...

Front seat mount held in place with 5 self tapping screws. Seat base is plastic so five screws are used to spread the stress...

Steering stop. We set it up so we could get as much lock to lock distance as possible for better manoeuvrability. Bars clear the tank by 10 mills. Stop is just tacked atm. Will only be welded in a couple of spots to reduce distortion of the botom of the steering head where outer bearing races will be installed once all welding is finished...

A happy owner-builder... Once the rear engine mount is made and tacked up, we will get the monster off the jig and onto its wheels... and that will be a great day!

Post now written up. On its wheels next week and then we'll get exhausts and muffler mounts made. Rear guard is also going to get bobbed. Wayne will then take it home and work on minor brackets and wiring.

Outer bearing races need to be installed in the steering head. Grease to prevent any damage as they slide in...

Races have been in the freezer for a few hours to shrink them. I bring them up to the workshop between two cooler bricks to keep them as cold as possible to the last moment...

I use a piece of 3/4" threaded rod with a nut and the right sized washer at each end to pull in the races. They often need a light tap with a small hammer on the edge initially to keep them lined up...

Front end on and on the floor. Measurements all worked and with suspension settled under its weight, bike is at height we planned... Wayne is very happy, especially with its overall appearance...

Up on the stand to do pipes. Here it has been levelled so we can get the two exhausts and mufflers even...

Wayne decided he wanted the tank a bit higher at the front. Aluminium spacer does the trick. Triumph badge will be removed to allow a trick paint job he has planned...

As you can see in the previous pic, we are using the original header pipes. They have been cut and tacked at the flange to realign them to the new frame, but need to be swung out another five mil at the bottom. We have also needed to extend them with a straight piece 75mm long.

You will see more complete posts on making up pipes for choppers, but we normally use mandrel bends as they are the cheapest way to construct a pipe time wise. This one has been marked to match the left hand extended header pipe...

Set square to make sure we don't have a kinky join!...

A quick tack and the alignment is correct. Need to cut the tack and reposition this one as it is one a bit crooked...

A length of straight pipe is welded to the mandrel bend just installed and then a slight bend upwards welded to that. Now the muffler. These are the stainless mufflers on the bike when purchased. They attached at a sharp angle to the header pipe. This is cut off...

... and a new piece of stainless is expanded to form a cone to match the hole. Other end also has to be expanded slightly to fit over the header pipe...

Welded on and slotted with an aircraft clamp to make a tight fit on the header...

Left side done. We still have to make a rear mounting bracket for the muffler that will double as a footpeg mount if ever needed. Pipes really compliment the bike and add to its flowing lines. Wayne really likes the nakedness of the bike and has canned the idea of using the original rear guard. We are hunting a 9" guard atm...

About time I finished this thread. The Trumpy has now gone home for wiring and assembling ready for final inspection by engineer. Here are the last couple of jobs done...

Exhaust Mounts...

Wayne is using a set of stainless after-market mufflers. They are unlikely to be quiet enough for The Man, but we are making mounts to suit them and will add any brackets needed for the ridiculous mufflers he will probably have to take it to Regency with.

First step is to set both mufflers at the same height and the same distance out from the swing arm. Distance out...

Height...

Left muffler is set up to match...

Next job is to make the brackets. They need to be strong enough to carry a lot of muffler, plus be used for footpegs if Wayne finds a willing passenger at a later date. Well with the sexy frame we have made, he shouldn't have too much trouble!!

After settling on a pattern, Wayne shapes up the brackets out of 10mm steel plate...

A piece of 1" flat bar is taped to the swing arm as a guide, so we can locate the brackets on each side of the bike. A piece of stainless is shaped up for each muffler. Thread is M10. The odd shape allows plenty of thread, but tapers to make the two welding surfaces more compatible...

Close up shows a little more shaping needed for a close fit...

Brackets tacked on to frame...

Wayne has been intrigued during the build as to the relative weights of the original versus our new frame. I think we definitely win out here. Showing the bracket we have replaced!!!

Last job I have photos of is fabricating the rear guard. That will be next...

Wide tyre required a 9" rear guard. Wayne wanted one with a valance, but the Indian company that makes these after market guards got a contract for a million rubbish bins and dropped all guard making to do the bins. I couldn't find any one that had one, so was able to pick up a 9" flat guard to which we can easily add valances...

First step is to set up our guard at the correct tyre clearance...

The guard needs some clearance to allow for tyre expansion at speed, slightly different diameters of various brands, so you can't just set the guard on top of the tyre. A couple of 10mm blocks taped to the tyre does the trick. Remember to only do this with an unworn tyre... or add another 5-10mm to allow for it...

Next step is to measure length of shocker when completely compressed and make up a strut at that length. This gives wheel position when you hit that massive pot hole and bottom out.

Wayne originally wanted to use his original guard, but realised it would look totally out of character (ie massive and excessively long) with the new look of his bike. So I had to bring in the guard mounts to match the width of out new guard. This is most accurately done by cutting half way through at the bends with an angle grinder and then bending with heat. The opened cuts will then be welded...

Wayne decided on cutting the guard length at 45 degrees to the axle. Here being marked square with a set square on the inside. Double check by using the set square on the other side...

Guard clamped in a special jig I made using some bent exhaust pipe as a cradle and a valve compressor to clamp the guard in place...

For some reason the guards never follow the radius of the wheel, so they need to be wedged and pulled in a bit. Here cut positions are marked...

Easily made little tool ensures the cuts are square to the guard radius. A single cut only is needed at each mark to pull in the guard sufficiently...

Wedged and welded. Holes are drilled at the front of the guard for mounting...

A couple of M8 nuts are welded to the inside of the guard. The guard is thick steel, but for longjevity, we welded in mudguard washers under the nuts to spread the weld contact area and spread stress. Threaded 6mm plates also welded to sides at rear for M6 mounting bolts. Anyone who has tried to remove or tighten a guard with the wheel still on will appreciate why we use captive threads on the inside...

Cardboard patterns are made until Wayne is satisfied with the result. Aftermarket taillight/number plate bracket shown where it will sit. Number plate overhangs guard to keep PC Plod of the rider's back...

Steel valences made and tacked in place. Clamp is used at each weld to keep guard and valence in line. Front mounting nuts can be seen...

Finished. Rear end is rounded for final finish. Wayne thrilled with the result. A couple more holes to drill each side and nuts welded inside the guard...

Final job was to finish welding the frame. Wayne then took it home for paint. A week later is was back to put the engine in and get it on its wheels. It is now back home getting wiring, and components installed. Once that is done, it will be inspected by the engineer, his paper work sent to Regency and a frame number provided. Then just a case of awaiting their ok and it is down there for final inspection.

We'll post a couple of photos here of the finished bike when it is done...

Fantastic results, Prof and Wayne. Can't wait to see it finished, in full paint'n'polish clothing. Been a very interesting build, with a lot of customising along the way.
I'm sure Wayne is wrapped with the bike, and the Engy shouldn't have any cause to knock it back. Top stuff guys.

Wayne brought the painted frame back to install the motor, which is a three person job.

We set the motor up on a bike jack. If you look closely behind the bike you will see the corner of a piece of 3mm flat sheet. We laid this across the bottom frame rails and slid the motor in...

To protect the paint we taped the frame. Turned out a big mistake. Wayne had used a matt rubberised paint advertised as a protection for ute trays. He assures me he followed preparation direct ions, but the paint just peeled off when we removed the tape!! I advised that we pull the motor and he repaint with a more standard black crinkle, but he's going to touch it up and see how it goes. Good thing we made it easy to remove the components, as I think he will be disappointed over time. How it protects a ute tray is beyond me. Anyone know why it peels so easily?

Triumph in the trailer and heading for home to wire up etc.

PS: Wayne dropped in a few days ago. Bike is finished and motor has been spun over. Just waiting on a missing electronics component and it will be ready for inspection.